Follow up report

[Terry, NJ]

Last week I asked whether or not a sagging frame might be straightened by jacking it up and trying to "sag" it off a fulcrum just behind the motor mounts.
Well, no! Not unless I have twenty years to wait. However, the idea remains sound. So to speed it up a bit, I used Brent's method of shrinking the bottom of the frame. Unfortunately, I don't have his level of skill and the experiment was not a 100% successful. However, I did get a small amount of correction.
The front of the hood no longer overlaps the grill at the bottom. Yet some angle of the hood is still there. The answer I think is Practice, practice, practice until I master the technique.
Coincidentally. There seems to be improvement in other areas Suddenly, my engine is running better and quieter. Slightly more power and a little higher top end. I doubt any connection, but who knows? I will try it again sometime.
Terry

[BRENT in 10-uh-C]

Terry, I apologize as I just saw this. One of the more difficult decisions in this task is determining where the stretch is. Since the body is still on the frame, you cannot use a laser or string to help find it. Therefore that may be part of your reason for less than perfect success.

Also, remember that while you must shrink the bottom, some of the side rail will need to be shrunk also. I think of that heated area as pie-shaped with the point at the top. The area that needs to be heated gets wider as you get closer to that bottom chord.

[Terry, NJ]

Brent, I didn't mention it, but another complication is the fact that there are hydraulic brake lines running along the frame on both sides. They are 3/16 and will take heat very quickly. I shielded them with a piece of old window channel, but I was still nervous about getting them too hot. Also, the torch I was using has no heating (welding) tip or a rosebud . I only had the cutting tip which only gives a very small, localized point of heat. Before I try this again, I want to have different equipment.
Terry

Originally Posted by BRENT in 10-uh-C

Terry, I apologize as I just saw this. One of the more difficult decisions in this task is determining where the stretch is. Since the body is still on the frame, you cannot use a laser or string to help find it. Therefore that may be part of your reason for less than perfect success.

Also, remember that while you must shrink the bottom, some of the side rail will need to be shrunk also. I think of that heated area as pie-shaped with the point at the top. The area that needs to be heated gets wider as you get closer to that bottom chord.

[GordonJ]

Terry - I bought an old frame to use as a buck while working on my body and body wood for the Deluxe Delivery I am restoring. It had a bad sag around the motor mounts. I followed Brent's guidance and I can tell you that it really works. Not that I doubted Brent, but I wanted to report what my results were using this method. I left the string stretched over the frame while I was heating the pie shaped section. When it was dull red hot, I sprayed it with a water bottle and literally watched the frame move towards the string! It took a 3/8" plus sag to about 1/16" sag in one application without any mechanical help. Since this is only a buck, it was good enough for me, but I am sure that if it was my final frame, I could have dialed it in to perfect...

[Special Coupe Frank]

Originally Posted by Terry, NJ

Brent, I didn't mention it, but another complication is the fact that there are hydraulic brake lines running along the frame on both sides. They are 3/16 and will take heat very quickly. I shielded them with a piece of old window channel, but I was still nervous about getting them too hot. Also, the torch I was using has no heating (welding) tip or a rosebud . I only had the cutting tip which only gives a very small, localized point of heat. Before I try this again, I want to have different equipment.
Terry

Terry, as I read this, I was thinking "he needs a Rosebud"...

Good luck with it !

Frank

[Special Coupe Frank]

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Brent, et al,

In correcting frame sag, has anyone finished-up leaving the frame slightly "proud" at the once-sagged area, to prevent future sag ?



SC Frank

[Kirby1374]

Originally Posted by Special Coupe Frank

Terry, as I read this, I was thinking "he needs a Rosebud"...

Good luck with it !

Frank

....rose..bud.....

great last word...

[BRENT in 10-uh-C]

Originally Posted by Special Coupe Frank

Terry, as I read this, I was thinking "he needs a Rosebud"...

Good luck with it !

Frank

Actually a cutting tip with a neutral flame is sufficient.

Originally Posted by Special Coupe Frank

Brent, et al,

In correcting frame sag, has anyone finished-up leaving the frame slightly "proud" at the once-sagged area, to prevent future sag ?



SC Frank

No need. They won't bend unless abused.

Originally Posted by 1930 coupe

How hot, purple, red, white?
How wide heat at the bottom, 2 inches? 1 foot?

It is not a 'one-shot' deal so work in small areas and gradually move the metal. The biggest thing is patience where after an area has been heated, allow it to return to room temps to see the exact progress.

Contrary to popular wisdom, the metal temp needs only to be hot enough to make steam when water is applied. It really does not need to be glowing red, purple, or any insanely hot color.

[Roger V]

This subject came up a few years ago (as do most topics). Marco mentioned it might be a good idea to make it slightly higher. I had a frame shop raise my frame 1/16". Will probably never know the long term effect.

Originally Posted by Special Coupe Frank

Brent, et al,

In correcting frame sag, has anyone finished-up leaving the frame slightly "proud" at the once-sagged area, to prevent future sag ?



SC Frank

[glenn in camino]

I like the idea of heat to shrink the metal, but I straightened the one from my sport coupe by chaining it down to one side of my lift and raising it with my floor jack. The sport coupe is now done and looks very straight. I'll try heat on my current project, a 28 roadster.